Flash power and tube lenght

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Pau
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Flash power and tube lenght

Post by Pau »

Small flash units like the built in camera ones have short discharge tubes and modest power while powerful units usually have long tubes in its big heads, although some low power units like ring flashes have long tubes.

My question is about any possible relationship between the discharge tube lenght and power in modern flash units.
For exemple, if you have several different flash units, can you relate the GN with the tube lenght?

The question may be relevant for use in a microscope illuminator train in the place of the halogen bulb. Because the illuminator is designed for a small light source with a long flash tube most flash light will be wasted, and if the power per lenght unit is the same in a small unit the actual illumination would be the same.

(I'm still thinking the desing of a flash/LED mixed iluminator likely closer to the Arturo's than the Charles one)
Pau

enricosavazzi
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Re: Flash power and tube lenght

Post by enricosavazzi »

Pau wrote:Small flash units like the built in camera ones have short discharge tubes and modest power while powerful units usually have long tubes in its big heads, although some low power units like ring flashes have long tubes.

My question is about any possible relationship between the discharge tube lenght and power in modern flash units.
For exemple, if you have several different flash units, can you relate the GN with the tube lenght?

The question may be relevant for use in a microscope illuminator train in the place of the halogen bulb. Because the illuminator is designed for a small light source with a long flash tube most flash light will be wasted, and if the power per lenght unit is the same in a small unit the actual illumination would be the same.

(I'm still thinking the desing of a flash/LED mixed iluminator likely closer to the Arturo's than the Charles one)
There seems to be no simple relationship between tube length (and diameter) if one compares the nominal power of flash units. Power is actually determined by the capacitance and charge voltage of the flash capacitors, so it is quite possible to feed a flash tube with a somewhat higher or lower power without noticing any immediate effects, other than the flash emission intensity. Also in the short term, a higher power requires a longer pause for cooling between flashes. In the long term, overloading a tube shortens its useful life. Extreme overloading may cause it to explode.

There is an extreme variability in tube length and diameter among studio flash units, especially low-power ones up to nominal 500 Ws. This is so because many of these units are overrated (the declared Ws is 2-3 times higher than the maximum physically possible power computed from the capacitor specifications and voltage) and built on a shoestring (the tube is relatively expensive, and therefore it is often underdimensioned). I suspect the same Wild West scenario applies to portable flash units.
--ES

Pau
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Post by Pau »

Enrico, many thanks for your answer. I'm sure you're right, there are too much variables.
But excuse me for resurrecting this post, it's still relevant for me.

I would like to know the lenght of the discharge tube of different power comparable flash units, in special of Canon modern speedlites.

If anyone can do aproximate measurements of the tube lenght of his Canon 270EX and/or 430EX or 580EX I will be most grateful
Pau

Chris S.
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Re: Flash power and tube lenght

Post by Chris S. »

Pau wrote:. . .Because the illuminator is designed for a small light source with a long flash tube most flash light will be wasted. . . .
Pau, I've wondered if an elliptical "holographic diffuser" could be used to efficiently reorient the light output of a flash tube from a line to an evenly-lit circle. To see what I mean, check out the graphics at the Edmund Optics page here. To view the interesting graphics, rather than a mundane shot of four filters in a line, click the "view more images" arrows below the box in the upper left portion of the page.

Some months ago, I picked up a discounted elliptical holographic diffuser to experiment in solving the same issue you're grappling with. Whether or not it will work, I still don't know, having left that line of inquiry in the long and ever-growing project queue.

--Chris

Babylonia
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Post by Babylonia »

Not used at little camera flashes but more general at studio flash-heads are flash tubes in a spiral shape, nearly round, or with a "hairpin" bend in it.
Overall dimensions however are far more big, than the tiny straight tubes of camera flashes. So I don't know if it helps you.

"Small" tubes of a bigger portable flash unit (still not a studio flash), e.g. of Quantum:
http://www.qtm.com/index.php?option=com ... Itemid=278
See shape of the spiral tube: http://graphics.qtm.com/images_products/250/282.jpg
Greetings from Holland

g4lab
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Post by g4lab »

There are guided arc flashlamps from Excelitas (formerly EG&G/Perkin Elmer) and Hamamatsu.

If you are building your own system to piggy back onto a halogen light source you should consider these. Hamamatsu is really pushing the power level up in them and also have units with internal reflectors which put out both collimated and focused beams.

http://jp.hamamatsu.com/products/light- ... ex_en.html

Excelitas also makes regular xenon flash tubes.
http://www.excelitas.com/ProductPages/Pulsed_Xenon.aspx

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